A.TTTB.SOSC.The spoken word URGENCYD.The spoken word PA……

单项选择题Messages concerning weather conditions transmitted by radiotelephone are preceded by（）.

A.MAYDAY
B.PAN-PAN
C.SECURITE
D.SOS

单项选择题The radiotelephone message that indicates a station is about to transmit a message concerning the safety of navigation or important meteorological warnings commences with（）.

A.TTT
B.The spoken word PAN
C.The spoken word SECURITE
D.XXX

单项选择题The Urgency Signal（）indicates that the station calling has a very urgent message to transmit concerning the safety of a ship or aircraft，or of some person on board or within sight.

A.SOS
B.XXX
C.TTT
D.PAN

单项选择题Which of the following indicates a grave and imminent danger requesting immediate assistance on radio telephone?（）.

A.SOS
B.Mayday
C.Securite
D.PAN

单项选择题Which one of the following is the safety signal?（）.

A.SSS
B.TTT
C.XXX
D.FFF